1. Field of the Invention
The present invention relates generally to axial-flow pumps and, more particularly, but not by way of limitation, to miniature axial-flow turbopumps such as may, for example, be used in miniature propulsion systems.
2. Description of Related Art
Pump-based propellant delivery systems have been used for propulsion engines where thrust values are greater than 50 kN. Technological limitations have largely prevented the development of miniature turbopumps. Such technical limitations include, for example, design challenges such as cavitation dynamics, throttling range and response time, mesoscale (sub-millimeter) manufacturing process, and inadequate design/analysis tools at smaller scales [1]. Generally, the relative importance of viscous effects (Reynolds number effects), rotor-stator clearances, surface roughness, measurement errors and misalignments increase as the size of the turbopump decreases [2-3]. Thus, scaling prediction becomes increasingly difficult at the millimeter scale. It is not clear whether presently available theories and design/analysis tools adequately predict flow dynamics and behavior of miniaturized turbopump systems [1-4].